#define _CRT_SECURE_NO_WARNINGS 1
#include <iostream>
#include <cmath>
using namespace std;

int main()
{
    int n = 0, m = 0;
    cin >> n >> m;
    cerr << n << m << endl;
    double result = pow(0.8, m) * pow(0.2, n - m);
    for (int i = 1;i <= n;i++)
    {
        result *= i;
    }
    for (int i = 1;i <= m;i++)
    {
        result /= i;
    }
    for (int i = 1;i <= n - m;i++)
    {
        result /= i;
    }
    printf("%.4f", result);
    cerr << result << endl;
    return 0;
}
